Residues from harvesting of tree nuts: An appraisal of energy value of walnut and almond husks

The husk of almond (Prunus dulcis, Mill.) and walnut (Juglans regia, L.) are co-products of two important shell fruits. Beside the extraction of antioxidants for nutraceutical and pharmaceutical applications, they could be targeted for energy aims. The recoveringpf such co-productscould improve the environmental and economic sustainability of nut cultivation. A better knowledge about the energy value can be useful in choosing if such biomass can address to a combustion plant or a biorefinery or left on the ground. In this study, the residual husks coming from the collection and processing have been characterized for the main energy parameters (moisture, calorific value, ash content, and elemental composition).Preliminary results showed that the residues are enough different for moisture, total solid, volatile matter and fixed carbon. Both the feedstocks contained a high amount of ashes, significantly higher in walnut than in almond. However, the higher and the lower heating value of the husk were comparable between the specie although for the walnut husk it was slightly higher. The higher value of C and the lower content of O in the almond husk make believe the latter have a better energy value.
Proceedings of the 27th European Biomass Conference and Exhibition, 27-30 May 2019, Lisbon, Portugal, pp. 303-306